Sensitizer for use in electrophotographic light-sensitive material

ABSTRACT

A sensitizer for use in an electrophotographic light-sensitive material containing an organic photoconductor comprising a pyrylium salt containing a carbazole nucleus represented by the following general formula (I);   wherein R1 represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, a haloalkyl group having from 1 to 5 carbon atoms a cyanoalkyl group having from 2 to 6 carbon atoms, a hydroxyalkyl group having 1 to 5 carbon atoms, or an acyl group; R2 represents a hydrogen atom, a halogen atom or a nitro group, R3 represents   R4 represents a hydrogen atom or a hydroxy group; or R3 and R4 when taken together form a substituted or unsubstituted benzene or naphthalene ring, said substituents being an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, a nitro group or a halogen atom; R5 represents a hydrogen atom or   R6 represents a hydrogen atom, a halogen atom, an amino group, an alkylamino group having from 1 to 4 carbon atoms or an alkyl group having 1 to 5 carbon atoms; X represents Cl , Br , I , ClO4 , No3 , HSO4 or BF4 .

United States Patent [1 1 Seoka et al.

[ 1 3,909,260 [4 1 Se t. 30, 1975 1 SENSITIZER FOR USE IN ELECTROPHOTOGRAPHIC LIGHT-SENSITIVE MATERIAL [75] Inventors: Yoshio Seoka; Syu Watarai;

Hisatake Ono, all of Asaka, Japan [73] Assignee: Fuji Photo Film Co., Ltd., Minamiashigara, Japan 22 Filed: Oct. 15,1973

21 Appl. No.: 406,267

[30] Foreign Application Priority Data Primary E.\'aminerNorman G. Torchin Assistant Examiner-J. P. Brammer Attorney, Agent, or Firm-Gerald J. Ferguson, Jr.; Joseph J. Baker [5 7] ABSTRACT A sensitizer for use in an electrophotographic lightsensitive material containing an organic photoconductor comprising a pyrylium salt containing a carbazole nucleus represented by the following general formula wherein R represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, a haloalkyl group having from 1 to 5 carbon atoms a cyanoalkyl group having from 2 to 6 carbon atoms, a hydroxyalkyl group having 1 to 5 carbon atoms, or an acyl group; R represents a hydrogen atom, a halogen atom or a nitro group, R represents R, represents a hydrogen atom or a hydroxy group; or R and R when taken together form a substituted or unsubstituted benzene or naphthalene ring, said substituents being an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, a nitro group or a halogen atom; R represents a hydrogen atom or R represents a hydrogen atom, a halogen atom, an amino group, an alkylamino group having from 1 to 4 carbon atoms or an alkyl group having 1 to 5 carbon atoms; X represents Cl, Br, I, C10 N0 HSO, 0r BF,.

7 Claims, No Drawings SENSITIZER FOR USE IN ELECTROPHOTOGRAPHIC LIGHT-SENSITIVE MATERIAL BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sensitizer for use in an electrophotographic light-sensitive material wherein an organic compound is used as a photoconductor.

2. Description of the Prior Art In electro photography where an organic photoconductor is used, the element most influencing the light sensitivity is a sensitizer.

As organic photoconductors for use in electro photography, polyvinyl hetero ring compounds represented by poly-N-vinyl carbazole; polynuclear aromatic vinyl polymers such as polyvinylanthracene; low molecular weight compounds having a hetero ring such as an oxazole nucleus, a thiazole nucleus, etc.; and the like, have been used heretofore.

However, these materials do not provide sufficient light sensitivity when used independently.

SUMMARY OF THE INVENTION The present invention provides an absolutely novel sensitizer which, when added to an organic photoconductor, improves not only the light sensitivity but also broadens the wavelength region to which the photoconductor is sensitive. More particularly, the present invention provides a sensitizer comprising a pyrylium salt having a carbazole nucleus.

DETAILED DESCRIPTION OF THE INVENTION The following various literature reports have been made on the synthesis of pyrylium salts:

a. Proceeding of the Indian Academy of Science, Section A, 37A, 544 550, (1953); (Chemical Abstracts, 48, 11402 (1954)) b. Proceeding of the Indian Academy of Science, Section A, 34A, 77 87 (1951); (Chemical Abstracts, 46, 11189 (1952)) c. Helvetica Chimica Acta, 39, 1 (1956), issued by Verlag Helvetica Chimica Acta; (Chemical Abstracts, 50, 6445 (1956) It has been found that, in the present invention, the

synthesis of the various pyrylium salts suitably used in the present invention can be by condensing (A) an ohydroxyarylaldehyde and a carbonyl compound or (B) one molecule of an arylaldehyde and two molecules of a carbonyl compound, in an inert solvent, such as a substituted aromatic hydrocarbon, e.g., nitrobenzene, chlorobenzene, etc., referenced in the above-described literature as one convenient process for synthesizing pyrylium salts.

That is, the various pyrylium salts can be synthesized by the above-described reaction (A) using an ohydroxyarylaldehyde represented by the following general formula (III) and a carbonyl group-containing carbazole derivative represented by the following general formula (II), or by the above described reaction (B) using a carbonyl group containing carbazole derivative represented by the following general formula (II) and an arylaldehyde represented by the following general formula (IV). Reactions (A) and (B) are schematically described below:

A. (Reaction between an o-hydroxyarylaldehyde (III) and a carbonyl group containing carbazole derivative (II) wherein R represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms (such as methyl, ethyl, propyl, butyl or pentyl), a haloalkyl group having from 1 to 5 carbon atoms (such as chloromethyl, chloroethyl, chloropropyl, dichloropropyl, chlorobutyl, bromomethyl, bromoethyl, iodomethyl, iodoethyl, fluoromethyl, fluoroethyl, and the like), a cyanoalkyl group having from 2 to 6 carbon atoms (such as cyanomethyl, cyanoethyl, cyanopropyl, cyanobutyl, cyanopentyl, and the like), a hydroxyalkyl group having 1 to 5 carbon atoms (such as hydroxymethyl, hydroxyethyl, hydroxypropyl, hydroxybutyl, hydroxypentyl, 2,3-dihydroxypropyl, and the like), or an acyl group (such as acetyl, propionyl, butyroyl, acetoacetyl, benzoyl, 2- carboxybenzoyl, and the like); R represents a hydrogen atom, a halogen atom (such as a chlorine atom, a bromine atom, iodine atom or a florine atom) or a nitro group; R and R each represent an alkyl group having from I to 5 carbon atoms (such as methyl, ethyl, propyl, butyl or pentyl), an alkoxy group having from 1 to 3 carbon atoms (such as methoxy, ethoxy or propoxy), a nitro group, a halogen atom (such as a chlorine atom, a bromine atom, iodine atom or a florine atom) or R are taken together to form a substituted or unsubstituted benzene ring or a naphthalene ring, in which the substituents are an alkyl group having 1 to 5 carbon atoms (such as methyl, ethyl, propyl, butyl or pentyl), an alkoxy group having 1 to 3 carbon atoms (such as methoxy, ethoxy or propoxy), a nitro group or a halogen atom (such as a chlorine atom, a bromine atom, iodine atom or a florine atom); and HX represents a Lewis acid such as HCl, l-lBr, HI; and X represents a Lewis acid anion such as Cl, Br", I, BE, etc.;

In the above process (A) the reactants are generally used in an equimolar ratio and the reaction is conducted in an inert solvent such as an ester (e.g., ethyl acetate, propyl acetate, butyl acetate, etc.; a cyclic ether (e.g., tetrahydrofuran, etc.) and the like. A suitable temperature is from about 1 C to 20C, preferably C to C with reaction times of about 5 minutes to 10 hours, more generally 10 minutes to 1 hour. A Lewis acid such as HCl, HBr and H1 is generally present during the reaction.

B. (Reaction between an arylaldehyde (IV) and carbonyl group containing carbazole derivative (II) wherein R R are the same as defined in reaction (A); R represents a hydrogen atom or and R represents a hydrogen atom, a halogen atom (such as a chlorine atom, a bromine atom, an iodine atom or a florine atom), an alkyl group having 1 to 5 carbon atoms (such as methyl, ethyl, propyl, butyl or pentyl), an amino group or an alkylamino group having 1 to 4 carbon atoms (such as ethylamino, methyl amino, propylamino, dimethylamino diethylamino and the like); and Lewis acid represents HCl, HBr, HCIO HNO H 80 BP or BF (C H O; and X represents a Lewis acid residue such as Cl, Br, 1", C10 N0 l-lSOf, or BF The reaction between an arylaldehyde and a carbonyl group containing carbazole derivative represented in the aforesaid reaction shematic (B) is conducted by dissolving both reactants in an equimolar amount in a solvent such as a substituted aromatic hydrocarbon solvent (e.g., nitrobenzene, chlorobenzene, etc.), at a concentration of about 1 to about by weight, preferably 2 to 10% by weight. adding thereto a Lewis acid, HX, such as HCl, HBr, HClO HNO H 50 BF or BF ,(C H O wherein X represents a Lewis acid residue such as Cl, Br, C10 N0 H50 or BF{, and heating the mixture to about 50C to about C for about 20 minutes to about 10 hours, more generally, 0.5 to 5 hours. After cooling the reaction mixture to a room temperature (about 15 to 25C), it is poured into diethyl ether to precipitate the crystals. The thus formed precipitate is filtered out to obtain the end product pyrylium salt. In the case of this reaction, however, it is necessary that the 3-position and the 6-position of the carbazole nucleus be substituted, respectively, by an acetyl group and a substituent other than a hydrogen atom.

The inventors have experimentally confirmed that, when a hydrogen atom is in the 6-position a triarylmethane dye will be formed under the same reaction conditions.

The above-described general formulae (LA) and (I-B) can be collectively represented by the following general formula (I);

R R -B) 1 2 wherein R represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms (such as methyl, ethyl, propyl, butyl or pentyl), an haloalkyl group having 1 to 5 carbon atoms (such as chloromethyl, chloro-ethyl, chloropropyl, dichloropropyl, chlorobutyl, bromomethyl, bromoethyl, iodomethyl, iodoethyl, fluoromethyl, fluoroethyl, and the like), a cyanoalkyl group having 2 to 6 carbon atoms (such as cyanomethyl, cyanoethyl, cyanopropyl, cyanobutyl, cyanopentyl, and the like), a hydroxyalkyl group having 1 to 5 carbon atoms (such as hydroxymethyl, hydroxyethyl, hydroxypropyl, hydroxybutyl, hydroxypentyl, 2,3-dihydroxy propyl, and the like), or an acyl group (such as acetyl,

propionyl, butyroyl, acetoacetyl, benzoyl, 2- carboxybenzoyl, and the like); R represents a hydrogen atom, a halogen atom (such asxachlorine atom, a

bromine atom, iodine atom or a florine atom), or a nitro group; Rgrepresents R represents a hydrogen atom, a halogen atom (such as a chlorine atom, a bromine atom, iodine atom or a florine atom) or an amino group or an alkylamino group having 1 to 4 carbon atoms (such as ethyl amino, methyl amino, propylamino, dimethylamino, diethylamino and the like),'an alkyl group'having l to 5 carbon atoms (such as methyl, ethyl, propyl, butyl or pentyl); and X represents Cl, Br, I, C10 N H80 or BF Preferred substituents for the pyrylium salts of this invention are for R a methyl group, an ethyl group or a hydrogen atom, for R a hydrogen atom or a bromine atom, for R a or a methoxy group, for R a hydrogen atom, or a group for R a methoxy group, a bromine atom, a nitro group' or a dimethylarriih'ogroup, and i for x-, cr, BF.,.,;or c10 Specific examples of the. compounds represented by the general formulae (l l),"(lll) and (IV), set forth in the reaction schematics (A) and (B), are illustrated below.

General Formula (II): Carbonyl group containing carbazole derivatives (II-l 3-Acetylcarbazole (II-2): 3-Acetyl-9-methylcarbazole (ll-3 3-Acetyl-9 ethylcarbaole (ll-4): 3-Acetyl-9-chloroethylcarbazole (II-5): 3-acetyl-9-hydroxyethylcarbazole (II-6): 3-Acetyl-9-cyanoethylcarbazole (II-7): 3,9-Diacetylcarbazole (II-8): 3-Acetyl-6 bromo-9-ethylcarbazole (ll-9): 3-Acetyl-6-chloro-9-ethylcarbazole (ll-10): 3-Acetyl-6:nitro-9-ethylcarbazole General Formula (III): o-l-lydroxyarylaldehydes (Ill-1 Z-HydroxybenZaldehyde (Ill-2): 2,4-Dihydroxybenzaldehyde (III-3 2-Hydroxy-3-methoxybenzaldehyde (III-4): 2-Hydroxy-3-bromobenzaldehyde (Ill-5 Z-Hydroxy-S-nitfobenzaldehyde (III-6): 2-l-lydroxy-a-naphthoaldehyde (III-7 l-Hydroxy B-naphthoaldehyde General Formula.,(-IV): Arylaldehydes (IV-1): Benzaldehyde (IV-3): 4-Methoxybenzaldehyde (IV-4): 2-Bromo'4-methoxybenzaldehyde (IV-5 Nitrobenzaldehyde (IV-6): Dimethylaminobenzaldehyde The reaction between an o-hydroxyarylaldehyde and a carbonyl group containing carbazole derivative represented in the aforesaid reaction schematic (A) is conducted by dissolving both reactants in an organic solvent such as ethyl acetate and, while cooling to about 5 to about 10C, saturating the mixture with a hydrogen halide under stirring. The reaction time is preferably about 10 minutes to about 1 hour. Upon leaving the reaction mixture for about 5 to about 15 hours, a pyrylium salt is precipitated as crystals. The thus formed precipitate is filtered out to obtain the end product pyrylium salt.

O: Ii

The synthesis of pyrylium salts in accordance with the above-described processes will now be described in greater detail by the following Synthesis Examples.

Synthesis Example 1 The absorption maximum wavelength of this compound in chloroform was 537 mp.

Synthesis Example 2 In the same manner as described in Synthesis Example 1 using 2-hydroxy-a-naphthoaldehyde (ill-6) and 3-acetyl-9-ethylcarbazole (ll-3), a pyrylium salt having the following structural formula was synthesized;

The absorption maximum wavelength of this compound in chloroform was 547 mu.

Synthesis Example 3 In the same manner as described in Synthesis Example 1 using 2-hydroxy-5-nitrobenzaldehyde (Ill-5) and 3-acetyl-9-ethylcarbazole (ll-3 a pyrylium salt having the following structural formula was synthesized;

The absorption maximum wavelength of this compound in chloroform was 574 mu.

Synthesis Example 4 In the same manner as described in Synthesis Example 1 using 2-hydroxy-a-naphthoaldehyde (III-6) and 3-acetyl-6-bromo-9-ethylcarbazole (ll-8), a pyrylium salt having the following structural formula was synthesized;

The absorption maximum wavelength of this compound in chloroform was 542 mu.

Synthesis Example 5 1.4 Grams of 4-methoxybenzaldehyde (IV-3) and 6.3 g of 3-acetyl-6-bromo-9-ethylcarbazole (ll-8) were dissolved in 50 g of nitrobenzene and, after adding thereto ml of boron trifluoride ethylate, heated for 2 hours over a water bath. Upon pouring the resulting reaction solution into a large amount of diethyl ether, a precipitate of compound formed was obtained. The precipitate was filtered out, washed with diethyl ether, and dried Furthermore, the product was extracted with ether, and the extract was concentrated to obtain the end product pyrylium salt as crystals. From the infrared spectrum thereof, acetyl group was found to have disappeared. Thus, the product appeared to have the following structural formula:

C ll

The absorption maximum wavelength of this compound in chloroform was 544 mp Comparative Synthesis Example The same procedures as described in Example 5 were conducted except for using 3-acetyl-9-ethylcarbazole (ll-3) in place of the 3-acetyl-6-bromo-9- ethylcarbazole. Thus, it was found that, since the 6- position is occupied by a hydrogen atom and is therefore reactive, a triarylmethane dye represented by the following structural formula was produced;

Patent App1ication Nos. .74489/70, 50966/72; and

On infrared spectral analysis this compound showed a peak at 1665 cm, characteristic of the acetyl group, and the absorption maximum wavelength of the compound in chloroform was 596 mu. Thus, the compound was tinged blue. (This compound also possesses a sensitizing effect on an organic photoconductive material, and is described in Japanese Patent Application No. 57400/72, (U.S Ser. N0-367,528,filed.lune,6,1973).

The thus obtained carbazole nucleus-containing pyrylium salts show efficient sensitizing effects on various organic photoconductive materials. In particular, they are effective fororganic photoconductive materials of 2 the carbazole system such as those described in U.S.

Pat. Nos. 3,206,306; 3,240,594; 3,240,595; and 3,704,119, British Patent 964,879, Japanese Patent Publication -Nos.. '14393/65, and 21054173, Japanese the like. The sensitizer of the present invention is added to an organic photoconductive material in an amount of based on the weight of the'organic photoconductive material; t 1

The organic photoconductive materials for "use in 'electro photography, sensitized with the sensitizer'of the present invention, can be processed in eithera dry manner or a wet manner. Specific processing procedures thereof are described in U.S. Pat. Nos.

2,221,776, 2,297,691 2,907,674, 3,081,263, 3 ,241, 998, and the like. For example, an organic photoconductive material such 'as poly-N-vinylcarbazole and the pyrylium salts of the present invention are dissolved in an organic solvent such as a halogenated hydrocarbon, e.g., chloroform, methylene chloride, ethylene chloride, and coated on the conductive support so that the dried thickness is about 5 to 50 microns using bar coating.

The present invention will nowbe described in greater detail by the following examples which, however, should not be construed as limiting the invention in any way. Unless otherwise indicated, all percents and parts are by weight.

EXAMPLE 1 -been subjected to electroconductivity-imparting processing (by coatingthereon Calgonite ConduetiyeP-olymer 261 (trade name'produced'by the Calgon- Corp.

and believed to have the followingstructure whereinn'represents a positive integer,-

at about 3 gfm Ina manner conventional in electrophotography; the thus obtained light-sensitive material wascharge'din the-dark,'imagewise exposed in an exposure amountof 1901-xlsec'using a white light-emitting source. Upon development-processing of the material, a distinct image was reproduced. Additionally, a developer comprising a carrier of nitrocellulose coated glass beads of a particle size of 0.4mm having adsorbed thereon a kneaded mixture of carbon black and polystyrene (5:5' by weight) was used.

The amount of the sensitizer (compound synthesized in Synthesis Example 1) added was varied and the appropriate exposure amount was examined. The results thus obtained are shown in the following Table 1.

Table '1 Amount of Pyrylium Exposure Amount Salt Added (mg) 7 (lxsec) .None 20,000 10 1,190

EXAMPLE 2 The pyrylium salt obtained in Synthesis Example 2 was added to 20 g of a poly-N-vinylcarbazole (as described in Example 1), and the sensitizing effect was examined in the same manner as described in Example 1. The results obtained are shown in the following Table 2.

Table 2 Amount of Pyrylium Exposure Amount Salt Added (mg) (lx'sec) None 20,000 I l 990 i '1 5 EXAMPLE 3 20 Grams of a poly-N-vinylcarbazole (as described in Example 1) and the compounds listed in Table 3 in the amount given therein were dissolved in 200 ml of methylene chloride. The resulting solution was coated on an aluminum-vacuum deposited polyethylene terephthalate film (Metalumy, made by Toray Industries, Inc.) in

a dry thickness of microns. In manner common in electro photography, the thus obtained light-sensitive materials were charged in the dark, exposed to a white light-emitting source through an original image, and subjected to a development processing using a liquid developer prepared by dispersing l g of a commercially available black offset ink of the following composition in 1 liter of cyclohexane.

Black Offset Ink Composition carbon black:

alkali blue toner*: rosin modified phenol-formaldehyde resin:

Boiled Linseed oil:

parts by weight 7 parts by weight 55 parts by weight 13 parts by weight HO oo Thus, distinct images were obtained. The appropriate exposure amounts are given in the followingTable 3.

Table 3 Exposure Amount Pyrylium Salt Amount Added (mg) (lx'sec) Synthesis 200 320 Example 3 Synthesis 200 330 Example 4 Synthesis 200 15 Example 5 wherein R represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, a haloalkyl group having from 1 to 5 carbon atoms, a cyanoalkyl group having from 2 to 6 carbon atoms, a hydroxyalkyl group having 1 to 5 carbon atoms, or an acyl group; R represents a hydrogen atom, a halogen atom or a nitro group; R

represents R represents a hydrogen atom or a hydroxy group; or R and R when taken together form a substituted or unsubstituted benzene or naphthalene ring, said substituents being an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, a nitro group or a halogen atom; R represents a hydrogen atom or R represents a hydrogen atom, a halogen atom, an amino group, an alkylamino group having from 1 to-4 carbon atoms or an alkyl group having 1 to 5 carbon atoms; X represents Cl, Br, I, ClOf, N0 H50 or BF{.

2. The electrophotographic light-sensitive element of claim 1, wherein said organic photoconductor is polyvinyl carbazole.

3. The electrophotographic light-sensitive element of claim 1, wherein said sensitizer is 17 18 4. The electrophotographic light-sensitive element of (1-4) claim 3, wherein said pyrylium salt is Br 5 UK N i 01" I N (1-5) O c1 0 H 5 5. The electrophotographic light-sensitive element of (I 5) claim 1, wherein said sensitizer is present in an amount of 0.0l to l5% by weight based on the weight of said organic photoconductor.

6. The eleetrophotographic light-sensitive element of claim 1 wherein said layer has a dried thickness of from 5 to 50 microns.

7. The electrophotographic light-sensitive element of claim 1 where said support is electrically conductive.

I i Ill 

1. AN ELECTROPHOTOGRAPHIC LIGHT-SENSITIVE ELEMENT COMPRISING A SUPPORT HAVING THEREON A LAYER OF AN ORGANIC PHOTOCONDUCTOR CONTAINING A SENSITIZER COMPRISING A PYRYLIUM SALT CONTAINING A CARBAZOLE NUCLEUS REPRESENTED BY THE FOLLOWING GENERAL FORMULA (1):
 2. The electrophotographic light-sensitive element of claim 1, wherein said organic photoconductor is polyvinyl carbazole.
 3. The electrophotographic light-sensitive element of claim 1, wherein said sensitizer is
 4. The electrophotographic light-sensitive element of claim 3, wherein said pyrylium salt is
 5. The electrophotographic light-sensitive element of claim 1, wherein said sensitizer is present in an amount of 0.01 to 15% by weight based on the weight of said organic photoconductor.
 6. The electrophotographic light-sensitive element of claim 1 wherein said layer has a dried thickness of from 5 to 50 microns.
 7. The electrophotographic light-sensitive element of claim 1 where said support is electrically conductive. 